Large Enhancement in Conductivity of Polyaniline Films by Cold Stretching

Abstract

The hot‐stretching method has been well accepted for enhancing the electrical conductivity of conducting polymer films. High temperature is the prerequisite to soften the polymer to highly align and elongate the polymeric molecular chains. In this study, the cold‐stretching method is proposed for the first time to enhance the conductivity of conducting polymeric films. Polyaniline (PANI) films are stretched at room temperature to different strain levels. It is observed that the applied strain has significant effects on the morphology, molecular chain structure, crystallinity, and crosslinking of the PANI films. As a result, the conductivity of PANI films is effectively increased by the cold‐stretching process. Particularly, a maximum conductivity with an 18.4‐fold increase in the direction parallel to the stretched direction is obtained when the elastic limit strain is applied. Compared to hot stretching, cold stretching is unique due to the extremely low dimensional change and very high efficiency achieved.magnified image

Synthesis and simultaneous enhancements in electrical and magnetic properties of oriented γ-Fe2O3-nanoneedle/PANI nanocomposite films by cold stretching

“…That is because the large stretching strain may cause partial damage of PANI chains as shown in Fig. 8e, and thus lower the crystallinity which is represented by the intensity of the characteristic peaks [28]. The trend of the change of peak intensity for XRD patterns is consistent with that of the conductivity (Fig.…”

“…6. It shows that the RT conductivity of the unstretched g-Fe 2 O 3 /PANI-HCl composite film is 2.1 S cm À1 , which is obviously lower than that (4.5 S cm À1 ) of the un-stretched pure PANI film doped with HCl [28]. It can also be seen that the conductivity in both directions increases with increasing the applied stress level until it reaches the maximum value at the elastic limit stress of 28.4 MPa (corresponding strain ¼ 0.60%).…”

“…The same observation was detected for the variance of the magnetic properties with increasing the applied stress level. [28]. However, when the applied stresses are higher than the elastic limit stress, deflections like micro-voids could be observed in Fig.…”

“…It can be seen that the intensity ratio (A k /A t ) of the absorbance peaks at 1593 cm -1 for N ¼ Q ¼ N stretching mode and 1301 cm -1 for CeN stretching mode, which can be used to characterize the vibrations along the PANI chain direction, increases with increasing the applied stress level [39,40]. That indicates that the PANI chains could have certain degree of orientation after cold stretching, which would bring about the increase in the conductivity [28,39,40]. respectively [42].…”

“…Particularly, a maximum conductivity with an 18.4-fold increase in the direction parallel to the stretched direction was obtained when the elastic limit strain was applied. Compared to the hot stretching, the cold stretching is unique due to the extremely low dimensional change and very high efficiency [28]. Inspired by this result, the cold-stretching process is applied here for enhancing the electrical conductivity of electromagnetic g-Fe 2 O 3 nanoneedle/PANI composite films.…”